Spermatozoa of Arnphiuma tridadijlum. By C. Johnston. 63 
before. And again the downward winding was resumed if the 
detention was only momentary. 
These reversals were frequently seen, and watched for some 
time. 
When at rest the spiral resolved itself into a most delicate 
modulating membrane, of about the width of the body at its upper 
part, and extending from the slight constriction behind the spindle- 
shaped head all along the body and tail. 
Of course we do not propose the dorsal membrane as a novelty, 
for that has been most thoroughly studied by Azermath and others ; 
but attention is asked to the head, formed of a lamina bent into an 
elongated cone, and presenting a projecting apicial filament ; to 
the twin cords of the body, apparently continuations of the tumid 
margins of the lamina, and supporting the dorsal arch; to the 
repeatedly observed reversal of the direction of the undulations of 
the dorsal membrane ; and to the , largeness of measure of the 
entire — creature, we had almost said — and of its several parts. 
But these last are hardly to be wondered at in Amphiuma 
tridactylum, the giant red corpuscles of whose blood, immediately 
fresh from the living creature, we have found to attain to such 
dimensions as of an inch in their long axis, of an inch in 
their conjugate diameter, by ^^V^ of an inch in thickness. These 
measurements were made with an eye-piece micrometer ; but we 
find them to overrate the size of the corpuscles upon comparison 
with a series of eleven superb photographs just executed by our 
distinguished friend Col. J. J. Woodward, M.D., and this day 
received from him. These pictures, taken with a Tolles' yV-inch 
objective, and a Tolles' inch, represent at once the disks and the 
micrometer, the divisions of which are rated at toW of an inch. 
By careful computation we find the larger disks to range from 
of an inch in length to -^^^ of the same measure. 
Our fraction of an inch refers to the largest fresh corpuscles 
we met with, and must be compared with Col. Woodward's 
of an inch for the same reason ; and if the latter be the true 
size of the greatest corpuscles, then our measurement of the 
spermatozoid of Amphiuma must suffer abatement in equal pro- 
portion. 
For the photographs and for the permission to use them we 
are happy to express our obligation to Col. Woodward. 
Note. — It is but fair to add that my measurements of Amphiuma s 
blood were made upon instantly recent blood-disks ; and that the 
photographs of Col. Woodward represented red corpuscles which 
had been preserved for thirty-six hours in a small vial deposited in 
a refrigerator, but which had a fresh appearance. 
Chr. J. 
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